Australia: The Land Where Time Began |
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Earliest Hominin Occupation in Sulawesi, Indonesia
Sulawesi is the largest island in Wallacea, the large zone of oceanic
islands that separates continental Asia from Sahul, the combined
landmass of Australia, including Tasmania, and New Guinea in the
Pleistocene
at times of low sea levels during glacial periods. An unknown hominin
lineage had colonised Flores by 1 million years ago, which is
immediately to the south (Brumm et
al., 2010), and by about
50,000 BP modern humans had crossed to Sahul (Clarkson et al., 2015;
O’Connor, 2015). Van den Bergh et
al. suggest that Sulawesi was probably pivotal in these dispersals,
on the basis of ocean currents, position and biogeographical context
(Morwood & Van Oosterzee, 2007). It is indicated by rock art in the
limestone karst region of Maros, southwest Sulawesi, where speleothems
have been dated by uranium series, revealed that humans were present on
the island at least 40,000 BP (Aubert et al., 2014). In this paper
van den Bergh et
al. report new excavations at
Talepu in the Walanae Basin to the northeast of Maros, where stone
artefacts have been found in situ
that are associated with fossil remains of megafauna (Bulbalus
sp.,
Stegodon and
Celebochoerus) were
recovered from stratified deposits that had accumulated from prior to
200,000 BP to about 100,000 BP. Sulawesi is suggested by these findings
to have hosted a long-established population of archaic hominins, as did
Flores, though their ancestral origins and taxonomic status has remained
elusive.
The discovery in the late 1940s in Walanae Basin, south Sulawesi of
‘Palaeolithic’ stone artefacts associated with fossil fauna dating to
the Pleistocene (Van Heekeren, 1949) led to a considerable amount of
speculation about the time depth of human occupation of the island
(Bartstra, Keates, Basoeki & Kallupa, 1991; Van Heekeren, 1972). The
lithic assemblages that were comprised of cores, choppers and flakes,
the ‘Cabenge Industry’, and derived from surface collections that were
not dated from along the eastern side of the Walanae River (Van
Heekeren, 1949; Bartstra,
Keates, Basoeki & Kallupa, 1991; Van Heekeren, 1972), which follows the
Walanae Depression, an elongated basin that is fault-bounded and trends
north-south. Van den Bergh et al.
recovered from the same unstratified contexts (Hooijer, 1948; Hooijer,
1974) the fossils of several extinct species, such as 2 pygmy
proboscideans, a giant tortoise, and a large endemic suid,
Celebochoerus, as well as
in excavations at various sites (van den Bergh, 1999). The stratigraphic
context and the time range of the ‘Cabenge Industry’ was still
unresolved because in situ
stone artefacts were still lacking (van den Bergh, 1999), in spite of
protracted investigations.
Surveys were conducted in the Cabenge area between 2007 and 2012 to
clarify these issues which led to the discovery of 4 new sites that
contained in situ stone
artefacts in their stratigraphic context. Deep-trench excavations were
undertaken at Talepu, one of the sites that were newly discovered. This
site is located 3 km to the southeast of Cabenge and 13 km downstream
from the point at which the Walanae River leaves the valley that
confines it and enters a widening floodplain that is subsiding actively
towards the north. East-west compression and wrench faulting along the
Walanae fault zone resulted in uplift of the Sengkang anticline and the
southern part of the Walanae Depression (Grainge & Davies, 1983;
Sukamto, 1975). The folded sedimentary sequences from the
Pliocene-Pleistocene of the Walanae Formation are now exposed in the
uplifted areas (van den Bergh, 1999). Accumulations of fluvio-lacustrine
sediments, dating to the Pleistocene to recent times, were facilitated
in the northern part of the Walanae Depression by compressional
down-folding. The Talepu site (4o 22’ 6.5” S, 119o
59’ 7” E) is situated near the hinge line between the southern part of
the Walanae Depression, which is uplifted, and the northern part, which
is subsiding.
The excavations were focused on the northernmost hill of an elongated
ridge near the village of Talepu that was about 600 m to the west of the
Walanae River. The summit of Talepu Hill is 32 m above sea level and 18
m above the adjacent floodplain of the Walanae River. There are deposits
exposed along this ridge comprised of a sequence of sub-horizontal
fluvio-lacustrine layers of sand and silt, which coarsens upwards, which
is overlain by alluvial cobble gravels. At Talepu 2 deep excavations
were carried out, trenches T2 and T4, which provided a combined length
of 18.7 m long stratigraphic section that exposed 5 main sedimentary
units: in descending order of depth, units A-E.
The first evidence of in situ
stone artefacts to be found in Walanae Basin in stratified and dated
contexts were revealed by these excavations. Van den Bergh et
al. recovered 270 stone
artefacts from between the surface and a depth of 4.2 m, which were
associated with the high-energy fluvial gravel deposits of unit A by the
T2 excavation. Most are therefore water-rolled to various degrees,
though 21 % are still in relatively fresh condition. Silicified
limestone cobbles that are coarse- to medium grained that have a
diameter of up to 130 mm, are the main source of raw material. Most are
flakes of medium- to large size, with cores that comprise 13 % of the
assemblage. Hard hammer blows to one face (42 %) were used to reduce
cores or bifacially (58 %) from striking platforms that were unprepared.
Reduction of cores was not intensive, though 7 cobbles were rotated and
multiplatform cores that were formed by subsequent reduction. Flakes
that were struck from the cobbles were then reduced to 1 face (60 %) or
bifacially (40 %). There is little evidence that the stoneworkers were
constructing tools of a specific form; rather sharp-edged flakes were
produced by stone flaking for use or a source for additional flakes,
though there is patterning in the flaking techniques.
From T4 the topsoil and colluvium to a depth of 120 cm contained 41
artefacts. There were, however, 4 silicified limestone artefacts
in situ in older strata that
were exposed within the silt of subunit E2, that provide the
earliest stratigraphic evidence at Talepu of human activity. 2
unmodified flakes, at 2.2-2.4 m depth, were recovered and there are 2
that are angular scatter fragments at a depth of 3.0-3.1 m, which van
den Bergh et al. suggest are
probably the results of percussion flaking. The scatter fragments are
made from distinctive mottled silicified limestone which appears to have
been removed from the same core. There is no evidence on the artefacts
of them undergoing transport by water, unit E not yielding any clasts
that are indicative of high-energy water flow.
There was only 1 fossil that was identified from T2: a lower molar
fragment of a bovid that was recovered from a depth of 4 m that is just
above the size range of the lowland anoa,
Bubalus depressicornis,
which is extant. 8
Celebochoerus dental
elements, e.g., a lower canine and 3 fragments of bone that were not
identifiable, were recovered from the silty interval of subunit E2
between 3.1 and 4.0 m below the surface and just beneath the deepest
stone artefacts. Van den Bergh et
al. suggest at least some of these fossil remains can be ascribed to
a single individual. A fragment of a milk molar from a
Stegodon was recovered
from a depth of 1.9-2.0 m and a dermal scute from a crocodile was
recovered from a depth of 3.9-4.0 m.
Teeth and bones that had been recovered from subunit E2 were dated by
uranium series by the laser ablation inductively coupled plasma mass
spectroscopy (LA-ICP-MS) methods (Grün et al., 2014), to constrain the
age of the deposits at Talepu. Sequential laser spot analyses were
carried out on cross-sections of 8 fossils of
Celebochoerus that had
been recovered from a depth of between 0.2-0.5 m below the deepest known
stone artefacts in the same silty unit. For each sample data sets were
combined and a single age estimate was calculated by use of the
diffusion-absorption-decay model (Sambridge, Grün & Eggins, 2012). There
were infinite error bounds for most of the age results, so minimum ages
were all that was possible (Grün et al., 2014). The fossil samples are
indicated by the combined uranium-series results to be older than
200,000 BP. Silty layers of units A, C and E have normal magnetic
polarities at all levels sampled based on palaeomagnetic samples. Taken
together with the results of uranium series analysis the fossils
therefore have an age of more than 200 ka and less than 780 ka.
In order to constrain the age of artefacts van den Bergh et
al. used a
multi-elevated-temperature post-infrared infrared stimulated
luminescence (MET-pIRIR) dating procedure (Li & Li, 2011; Li, Jacobs
Roberts & Li, 2014) was applied to feldspar grains that were rich in
potassium that had been extracted from 5 sediment samples that spanned
the entire sequence. The ages in stratigraphic order obtained for the 4
samples from T2 that were analysed are 103 ±
9 ka at a depth of 3 m to 156 ± 19 ka at 10 m depth. The Talepu
cultural sequence ends at about 100 ka, or possibly earlier, as
suggested by these results. Sediments dating to 156 ± 19 ka were
deposited near the top of unit D, which lies above the sedimentary layer
unit E from which the deepest artefacts were recovered, more than 3 m
below. The oldest evidence for stone artefacts from Talepu that is
securely dated therefore has an age of 194 to 118 ka at the 95 %
confidence interval (2σ), though it is clear that the site was occupied
earlier given the recovery of artefacts from the greater stratigraphic
depths. In the lower trench, T4,
a sample recovered from a depth of 8 m was found to have a minimum age
of about 195 ka. This estimate of age is stratigraphically consistent
with the MET-pIRIR ages for the T2 and with the minimum uranium ages of
about 200 ka for the T4 fossil remains from subunit E2.
It is suggested by the results of the Talepu excavation that it is now
possible to conclude that the initial occupation of Sulawesi occurred at
least 118 ka. As earlier assumptions had Sulawesi being only colonised
by
H. sapiens, which are
believed at present to have arrived in the region by about 50,000 BP,
the identity of these earlier inhabitants is of great interest. In
island Southeast Asia the earliest skeletal remains of
H. sapiens are from about
45,000 BP (Barker et al., 2007; Grün et al., 2005), though in the Levant
(Grün et al., 2005) the earliest modern skeletal human remains have been
recovered that date to about 120 ka, and possibly a similar time in
Southeast Asia (Westaway, 2007). It appears possible, though
controversial, that soon after
H. sapiens evolved in
Africa they spread to Sunda, the easternmost tip of continental Asia and
by about 120 ka they crossed to Wallacea. However, by 1 million years
ago early hominins had already reached Flores, which is far smaller and
more remote than Sulawesi, van den Bergh et
al. suggesting that they
possibly arrived on Flores on debris from a tsunami (Morwood & Van
Oosterzee, 2007). Therefore it is conceivable that the first humans on
Sulawesi could possibly have arrived in a similar manner at around the
same time or earlier or later.
The findings from Talepu attest to the presence on Sulawesi of early
tool makers by the Middle Pleistocene, though a definitive answer as to
which species of hominin was the first to arrive is precluded by the
lack of human fossils dating to the Pleistocene. Van den Bergh et
al. say there are at least 3
candidates in the region of potential island colonisers: the known and
inferred distributions of
H. floresiensis on
Flores, about 190 ka or earlier (Brumm et
a;., 2010), on the southern
margin of Sunda (Java of the present),
H. erectus, about 1.5
million years ago to about 140 ka (Zaim et al., 2011; Indriati et al.,
2011), and ‘Denisovans’, who are suggested by van den Bergh et
al. to have possibly extended
into Wallacea (Cooper & Stringer, 2013). When the currents of the
Indonesian through-flow that are predominantly southerly flowing
(Sprintall, 2014), van den Bergh et
al. speculate that Borneo to
the west, which was part of mainland Asia at times of low sea level is
the most likely point of origin for the colonisers of Sulawesi, and to
the north the Philippines, the northern extremity of Wallacea, with the
implication that there may be records of archaic hominins on other
islands in the region that are still to be discovered.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |